Structure of gas sensor ensuring quick activation and mechanical strength

Abstract

A gas sensor element includes a solid electrolyte plate, a measurement gas-exposed and reference gas-exposed electrodes affixed the solid electrolyte plate to define a sensing portion, and a heater. The heater includes a heating element attached to a heater substrate in a given pattern which has a heating area S 1 . The solid electrolyte plate has a sensing area S 2 in which the sensing portion is provided. The areas S 1 and S 2 are selected to meet a relation of S 2 /S 1 ≦0.9, thereby ensuring the heating efficiency of the heater without sacrificing a minimum required size of the area S 1 of the solid electrolyte plate or a desired mechanical strength of the gas sensor element.

1 . A gas sensor element having a length comprising: 
 a solid electrolyte plate;    a measurement gas-exposed electrode affixed to a surface of said solid electrolyte plate;    a reference gas-exposed electrode affixed to a surface of said solid electrolyte plate;    a sensing portion defined by said measurement gas-exposed electrode, said reference gas-exposed electrode, and a portion of said solid electrolyte plate through which said measurement gas-exposed electrode and said reference gas-exposed electrode are opposed to each other; and    a heater including a heater substrate joined to said solid electrolyte plate and a heating element affixed to the heater substrate in a preselected pattern,    wherein the pattern of the heating element occupies an area S 1  on the heater substrate which is defined by a first, a second, a third, and a fourth line, the first and second lines extending in a width-wise direction of the gas sensor element through ends of the pattern in a lengthwise direction of the gas sensor element, the third and fourth lines extending in the lengthwise direction of the gas sensor element through ends of the pattern in the width-wise direction of the gas sensor element,    and wherein said solid electrolyte plate has an area S 2  defined by a fifth and a sixth line which extend in the width-wise direction of the gas sensor element through ends of said sensing portion in the longitudinal direction of the gas sensor element, the areas S 1  and S 2  being selected to meet a relation of S 2 /S 1 ≦0.9.    
   
   
       2 . A gas sensor element as set forth in  claim 1 , wherein the areas S 1  and S 2  are selected to have a relation of 0.4≦S 2 /S 1 ≦0.7.  
   
   
       3 . A gas sensor element as set forth in  claim 1 , further comprising an alumina material disposed between said solid electrolyte plate and the heating element.  
   
   
       4 . A gas sensor element as set forth in  claim 1 , wherein said solid electrolyte plate and the heating substrate constitute a body of the gas sensor element which has a length with a sensing side end on which said sensing portion is provided and a sensor output side end opposed to the sensing side end, and wherein the sensing side end has a transverse sectional area smaller than that of the sensor output side end.  
   
   
       5 . A gas sensor element as set forth in  claim 4 , wherein the body has a transverse sectional area which increases continuously from the sensing side end toward the sensor output side end.